The present invention relates generally to a passenger conveyor and, in particular, to an apparatus for stopping a passenger conveyor in response to the application of a predetermined force on a comb plate of the passenger conveyor.
United States safety regulations (ASME A17.1/Rule 805.1) require that an escalator or a moving walkway must be stopped by actuating a safety switch when, as a consequence of an obstruction, an horizontal force acting on a comb plate exceeds a value of 500 newtons or a vertical force acting on the comb plate exceeds a value of 668 newtons for each side. This regulation has the consequence that existing safety equipment must be modified and new safety equipment must be constructed in conformity with the regulations.
The U.S. Pat. No. 5,398,800 shows a safety device for actuating a safety switch when a carrier plate of a people mover is displaced in either the horizontal direction or the vertical direction. The safety switch triggering equipment includes an horizontally extending switching rod tensioned by a compression spring and a safety switch. A pivotable angle lever is coupled as an intermediate member between the carrier plate which has comb segments and the switching rod. Upon movement of the carrier plate in an horizontal direction, the triggering of the safety switch takes place since the angle lever accompanies the movement to move the switching rod although the lever is not rotated. Upon a vertical movement of the carrier plate, the angle lever is rotated to move the switching rod. The triggering travels are settable by means of set screws and the triggering force is settable by means of variable spring tension. The ratio of the horizontal to the vertical triggering force is defined solely by the geometric dimensions, the lever arm lengths, of the vertically and horizontally extending arms of the angle lever. In addition to this triggering equipment, the front part of the comb plate is formed to be somewhat movable and can actuate a signal-generating pressure hose in the case of a force applied in the vertical direction.
The invariable fixed ratio of the horizontal to the vertical triggering forces in the above described safety device is restrictive. The indirect transmission of the vertical movement of the carrier plate to the triggering equipment by the angle lever produces additional friction and can, also as a consequence of wear, disadvantageously influence the reproducibility of the triggering forces in both the vertical and the horizontal directions.